objective-c - 跳过痛苦的 Core Data 迁移并迁移到新的数据模型

Question

当我什至不关心旧数据时，我花费了大量时间将核心数据整理到新的迁移中。有没有一种方法可以删除所有现有数据并跳转到新的数据模型，而不是每次更改数据模型时都处理映射模型的麻烦？

Answer 1

是的，只需删除存储文件并重新创建它即可。我经常(至少在开发过程中)让我的代码尝试自动迁移，如果失败，则清除商店并重新开始:

// storefile is an NSURL to the store file, mom is the NSManagedObjectModel
NSError *err = nil;
NSPersistentStoreCoordinator *psc = [[[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:mom] autorelease];
[psc addPersistentStoreWithType:NSSQLiteStoreType
                  configuration:nil
                            URL:storefile
                        options:[NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithBool:YES],
                                 NSMigratePersistentStoresAutomaticallyOption,
                                 [NSNumber numberWithBool:YES],
                                 NSInferMappingModelAutomaticallyOption,
                                 nil]
                          error:&err];
if (err) // could be more specific about testing this error
{ // assume automigration failed, blow away the store and try again
  err = nil; // log it first!
  [[NSFileManager defaultManager] removeItemAtURL:storefile
                                            error:nil];
  [psc addPersistentStoreWithType:NSSQLiteStoreType
                    configuration:nil
                              URL:storefile
                          options:nil
                            error:&err];
}
// then test err again and give up if there's still a problem